Gaspar de Quesada (died April 7, 1520) was a Spanish explorer who participated in Magellan's circumnavigation as captain of the Concepción, one of the expedition's five ships.
Approximately six months in to the expedition, Quesada, with two other Spanish captains, attempted to overthrow Magellan in the Easter mutiny at the South American port of St. Julian.
During a stop at the Canary Islands, Magellan received a secret message from his father-in-law, Diogo Barbosa, warning him that the Spanish captains were planning to mutiny.
When the weather conditions became intolerable, the fleet anchored on March 31, 1520, at a natural harbor they called Saint Julian, located in modern-day Argentina.
The mutiny began around midnight of April 1, when Quesada and Cartagena covertly led thirty armed men aboard the San Antonio, moving from the Concepción in a skiff.
They seized control of the San Antonio, with Quesada stabbing and mortally wounding Juan de Elorriaga, the ship's master, who resisted the mutineers.
Magellan successfully fought back against the mutineers, first by having Mendoza killed and taking control of the Victoria, then blocking the harbor to prevent the Concepción and San Antonio from escaping.